The presents invention relates to the domain of chemistry and more particularly to that of human or veterinary therapeutic chemistry.
The present invention especially concerns the use of porphyrin for the production of a medicine lowering the number of eosinophils.
In fact, many illnesses or pathologies are connected with hypereosinophilia; amongst them, bronchial asthma can be particularly cited.
The morbidity of this illness remains significant. In France the number of people affected by asthma is calculated at 2.5 million, and the number of deaths directly attributable to asthma is 2000 per year (cf. Epidemiological study of the European Community Respiratory Health Survey). The prevalence of asthma thus remains worrying, whatever is the age and geographical location of the population studied, The treatment of chronic asthmaxe2x80x94apart from acute attacksxe2x80x94is mainly dominated by the use of xcex22-stimulants and corticosteroids administered by inhalation. Antihistamines are only marginally used today. Each category of medicines causes a different type of effect:
The xcex2-stimulant agents essentially cause the relaxation of the smooth bronchial muscles: they also reduce the liberation of mediators. These substances including adrenaline, isoproterenol as well as more selective substances of the xcex22 receptors (bronchial tubes) than the xcex21 receptors (heart). After inhalation, the xcex22 (xcex22-adrenergic) substances act very quickly (in several minutes) but are only active for several hours.
The principle mode of action of theophylline is the relaxation of the smooth bronchial muscle. It inhibits the delayed phase of allergy and inhibits the liberation of inflammation mediators by mastocytes. Many authors consider that it is currently the most effective maintenance treatment for asthma. One of its major drawbacks however, is its narrow therapeutic margin.
Corticosteroids inhibit the migration of granulocytes towards the sites of allergic reaction, and prevent the liberation of inflammation mediators. In particular, when they are administered in aerosols, they inhibit the delayed phase of the allergy (but not the immediate phase) and the resulting bronchial hyperactivity. Although they are very effective, the systematic administration of corticosteroids has to be reserved for difficult cases because of their secondary effects. Inhaled steroids are used for maintenance treatment but not for acute asthma attacks.
Sodium cromoglycate and nedocromil are used as a preventive measure. They inhibit the liberation of mediators and reduce bronchial hyperactivity. Cromoglycate appears to be most effective in children and certain adults, for the maintenance treatment.
Subcutaneous specific desensitisation has been used for almost a hundred years; however the way it works is still not completely understood. The injection of allergens must be carried out under medical supervision. The results of desensitisation are controversial and only appear to improve the condition of a fraction of asthmatic people.
Anti-leukotrienes are currently the cutting edge in the domain of new therapies for asthma. The leukotrienes are synthesised by the inflammation cells. They play a role in the recruitment of inflammation cells and in bronchoconstriction. A number of molecules capable of inhibiting the effect of leukotrienes are currently being developed. Two of them, zafirlukast and pranlukast, are antagonists of the leukotriene receptors, but their use remains limited to moderate cases of asthma.
The importance of phosphodiesterases inhibitors, the main one being theophylline, is currently being rediscovered. The developed drugs currently attempt to inhibit more specifically phosphodiesterase of type IV, preponderantly present in the inflammation cells (eosinophils, lymphocytes) and the smooth bronchial muscles. The second-generation theophyllines are better able to be tolerated than theophylline itself, whose therapeutic margin remains narrow.
Furthermore, monoclonal antibodies directed against IL-5 are developed in the aim of controlling hypereosinophilia and the bronchial hyperreactivity of asthma. Even so, anti-IgE monoclonal antibodies are developed in the aim of blocking the IgE responsible for the sensitisation of the allergy cells. However, the effectiveness of these products in human asthma still has to be proven.
Asthma has been defined as xe2x80x9ca chronic inflammatory illness of the airways, responsible for attacks of wheezing, a reduction of the MEVS (Maximum exhalation volume per second) and bronchial hyperreactivityxe2x80x9d (NIH workshop report, January 1995). Bronchial hyperreactivity is the tendency that the bronchial tubes in asthmatics have to contract under the influence of a number of irritant or pharmacological stimuli, which are without effect in a healthy subject.
The most spectacular characteristic of the histopathology of asthma is the very large infiltration of eosinophils, macrophages and lymphocytes into the bronchial mucous membranes. Eosinophils appear to be the key cells responsible for lesions of the bronchial mucous membranes and bronchial hyperreactivity, although the precise mechanism of these phenomena is still being discussed.
Recent studies have compared asthmatics with healthy volunteers by using the broncho-alveolar wash technique and carrying out bronchial biopsies. A high number of eosinophils, both in the bronchial mucous membranes and in the broncho-alveolar wash fluid, is characteristic of asthma. Blood hypereosinophilia and the presence of eosinophils in the sputum, are characteristic of asthma; the level of eosinophils in the blood is correlated to the level of bronchial hyperreactivity.
After their differentiation and maturation in the bone marrow, the mature eosinophils are liberated into the blood circulation and go on to their main location in the tissues. The life span of the eosinophils in the tissues is unknown, but it is estimated at at least several days and it is probably dependent on the presence of cytokines like IL-5, IL-3 or GM-CSF. In some tissues (Skin, lung), the eosinophils are physiologically rare, but they can migrate to these tissues where they display their cytotoxic function and liberate inflammation mediators in response to a suitable stimulus [Texeira et al, 1995, Tr. Pharmacol. Sc. 16:418-423].
Eosinophils contribute to the physiopathology of allergic illnesses, particularly in the skin, the lungs, the nasal and ocular mucous membranes [Corrigan et al, 1992, Immunol. Today 13:501-506].
The accumulation in the tissues of eosinophils during allergic illnesses can prove to be disastrous; in fact, the granular proteins of the eosinophils are cytotoxic for the bronchial epithelial cells and also have many effects on the mastocytes, the epithelial cells, the macrophages and the T cells. Many works stress the link between the number of eosinophils, their state of activation and the severity of the asthma, both in man and animals (Bousquet et al, 1990, N Engl. J. Med. 323:1033-1039; Roisman et al, 1995, J. Clin. Invest. 96:12-21).
However despite the progress made in the course of the last few years, in the understanding of the mechanisms of allergy in general and asthma in particular, the most used medicines today belong to therapeutic classes which have been available for decades and the new molecules on the market continue to be based on old concepts.
According to the present invention, the proposed medicine is based on a different concept, that of preventing the accumulation of eosinophils in the tissues by pharmacologically acting on their life span. In fact, having the possibility of pharmacologically modulating the life span of the eosinophils is essential as it affects the potential of the eosinophil to liberate mediators, to exert its cytotoxicity or to functionally co-operate with other cells. Cytokine IL-5 appears to play a very important role in the survival in vivo of the eosinophils. It is however pharmacologically worthwhile to inhibit the effects of IL-5 and other factors for the survival of the eosinophils. This pharmacological modification of the life span of eosinophils has been little explored until now.
U.S. Pat. Nos. 5,510,339 and 5,631,267 (Gleich et al) concern the use of lidocaine as well as other local anaesthetics in the treatment of asthma. These authors indicate that in vitro lidocaine and other local anaesthetics reduce the survival of eosinophils. The inhalation of lidocaine thus makes possible the reduction of glucocorticoids inhaled, in asthmatics.
In the absence of survival factors (IL-5, IL-3 or GM-CSF . . . ), the eosinophils in culture in vitro quickly die (in 48-72 hrs) by an active phenomenon of xe2x80x9cprogrammed cellular deathxe2x80x9d which has the characteristics of apoptosis. Apoptosis is the opposite of necrosis which results in a massive attack of the cell leading to cellular lysis thus accompanying inflammatory phenomena. In the course of apoptosis, on the other hand, cellular homeostasis continues and membrane integrity is maintained. The apoptotic cell is rapidly recognised (because of the expression of certain membrane antigens) and phagocytized by macrophages or by surrounding cells. The apoptotic cell therefore plays a role in its own death (xe2x80x9ccellular suicidexe2x80x9d).
So, the induction of the xe2x80x9cprogrammed cellular deathxe2x80x9d of the eosinophils (apoptose) is not accompanied by inflammation and on the contrary suppresses the inflammation linked with tissue hypereosinophilia; that is why the pharmacological induction of the death of the eosinophils by apoptosis is a worthwhile process. The direct consequence of the induction, of the apoptosis of the eosinophils is the reduction of the number of eosinophils in the tissues.
However, the pathways of intracellular signals which lead cells to apoptosis are shared by many cells. So, the problem that arises is how to specifically induce the apoptosis of the eosinophils without inducing that of the cells of the respiratory epithelium and mucous membranes, and consequently without being toxic for the body.
In a surprising manner it has been found according to the present invention that Zinc-Protoporphyrin IX (ZnPP-IX) has the property of inducing the eosinophils without being toxic for the body.
ZnPP-IX is a natural molecule that is particularly present in the red blood cells. Its main chemical characteristics are the following:
Appearance: dark red
Molecular weight: 626.1
Basic formula: C34H32N4O4Zn
Storage: xe2x88x9220xc2x0 C., stable for at least 1 yearxe2x80x94protected from light and humidityxe2x80x94
Solubility: in ethanol (10mg/ml), DMSO (20mg/ml), very soluble in aqueous alkaline solutions
Formula developed: 
No toxicity has been reported in animals as far as ZnPP-IX is concerned.
Table I below gives the toxicity of ZnPP-IX and the doses used in the litterature (in vivo animal studies). Three species were used: rats, mice and monkeys. Several methods of administration were used: intravenous (i.v.), intraperitoneal (i.p.) and sub-cutaneous. No harmful effects were revealed.
The present invention therefore specifically concerns the use of Zinc-Protoporphyrin IX (ZnPP-IX) or one of its salts, for the production of a medicine intended to reduce the number of eosinophils in the tissues.
Zinc-Protoporphyrin IX (ZnPP-IX) can be used for example as a disodic derivative.
Amongst the pathologies linked to hypereosinophilia, bronchial asthma, atopic dermatitis, allergic rhinitis and allergic conjunctivitis can be cited.
In fact the physiopathology of allergic rhinitis and asthma are one and the same. In both cases it is the recruitment of-eosinophils in the respiratory tissues.
Allergic conjunctivitis is often linked with allergic rhinitis. Although it is less studied on a fundamental level than asthma and allergic rhinitis the importance of the mastocyte-eosinophil coupling in allergic rhinitis is stressed. During atopic dermatitis, there is a massive recruitment of eosinophils in the dermis. There are massive deposits of cationic proteins from the eosinophils and relatively few intact eosinophils (Leiferman K. M., J. AM. Acad. Dermatol. 1991, 24: 1101-1112). In fact, they undergo lysis very rapidly (necrosis).
According to the invention, therefore, Zinc-Protoporphyrin IX (ZnPP-IX) is used for the production of a medicine intended to treat pathologies linked to hypereosinophilia.
More specifically, ZnPP-IX is used according to the invention for the production of a medicine intended to treat bronchial asthma, atopic dermatitis, allergic rhinitis, and allergic conjunctivitis.
ZnPP-IX could be used in association with any other active ingredient intended to treat the pathologies linked to hypereosinophilia. Examples of such active ingredients are corticosteroids, xcex22-mimetic agents, antileukotriene, lipoxygenase inhibitors, PAF-acether antagonists, synthetic PAF-acether inhibitors, synthetic prostaglandin inhibitors, anti-H1, anti-degranulation agents like sodium cromoglycate, the antagonists of substance P, VIP, bradyknin, CGRP, the antagonists of IL-5 and the anti-IL-5 monoclonal antibodies, or any immunotherapeutic treatment allergenic or otherwise. ZnPP-IX is used in association with inert, non-toxic, pharmaceutically acceptable excipients or vehicles, allowing oral, topical, parenteral, nasal or bronchial administration. ZnPP-IX can be used in the form of an aqueous solution or suspension, or in a dry state, in plain or sugar coated tablets, soft gelatine capsules, capsules, powders. For asthma, the preferred method of administration is by inhalation.
As a general rule, the content in ZnPP-IX can vary from 0.050 mg to 5000 mg per unit dose.